Is There a Shortcut to Make a Bezier Curve Straight
Can you make your question more clear, what do you mean make it straighten?
Do you mean you want to "unwrap" it as in keeping it's length and making it linear, or do you want to make individual segments linear?

You can either use the toolbar button Set Spline Type to make a whole spline into a Polyline that will force all segments to be lines, or you can select a bunch of vertex and press V to access the Handle Type menu and make selected vertex into Vector type that will make segments between them straight.

Alternatively if you just want to make a 2D "planar" spline you can just press the 2D button in the Properties Window>Object Data Tab of your bezier curve object.